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Pooja Mohanty, Dillon Brown, Reece Mazade, Machelle T Pardue; Rod pathway signaling has protective effects on myopia susceptibility in dim, but not bright light.. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1395.
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© ARVO (1962-2015); The Authors (2016-present)
Bright ambient light has protective effects on the development of myopia. Recently, we have shown that in addition to bright light, dim ambient light is also protective in a mouse model of myopia, while intermediate, indoor ambient light was not (Landis et al., IOVS 2021). Since rod photoreceptor pathways can still be active in bright light conditions (Tikidji-Humburyan et al., Nature Comm 2017), we investigated the role of the rod pathway signaling in the protective effects of dim and bright light against lens-induced myopia (LIM) using transgenic mice that only have functional rods.
We developed an in-house breeding colony that produced mice with a “rod only” genotype: rod transducin α Gnat1+/+, cone transducin α Gnat2-/-, and melanopsin Opn4-/-. Myopia was induced by affixing a -10D lens over the right eye starting at postnatal day 28; naïve left eyes were used as contralateral controls. Mice were housed in dim (1 lux), indoor (50 lux), or bright (10,000 lux) lighting for the entirety of lens wear. In each light group, we compared LIM mice (n=3) to naïve littermate controls (n=4). Refractive error, corneal curvature, and ocular axial parameters were measured weekly until 3 weeks post-LIM.
Under all light levels, “rod only” mice with LIM developed significant refractive shifts (difference in refractive error between right and left eye) compared to naïve controls (p<0.02). However, the ambient light level significantly influenced the magnitude of LIM development (two-way RM ANOVA, p<0.001). Similar myopic shifts developed in the indoor (-6.95±0.05D) and bright light (-6.69±0.61D) groups (p=0.99). However, mice housed in dim light had a reduced myopic shift (-4.22±0.32) that was significantly different from mice housed in indoor lighting (p=0.04). No differences were found between groups for corneal curvature or ocular axial parameters.
“Rod only” mice were able to respond to lens defocus under all ambient light conditions, suggesting that rod pathways are sufficient to detect the myopigenic signal. In the absence of cone and melanopsin function, bright light was not found to be protective on myopia development. However, rod pathways appear to underlie the protective effects of dim light on myopia. Future research will determine the selective contribution of cone and melanopsin pathway signaling in the protective effects of bright light on myopia.
This is a 2021 ARVO Annual Meeting abstract.
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